Conventional multimedia memory card (MMC) has been disclosed by U.S. Pat. No. 6,040,622. As shown in FIG. 1A (PRIOR ART), the MMC 1 comprises a package 10 embedded in a lid 11 wherein conductive terminals (or gold fingers) 101 formed on a bottom surface 100a of a substrate 100 of the package 10 are exposed to the atmosphere, and the MMC 1 has a chamfer 13 for identifying a direction of application.
As shown in FIG. 1B (PRIOR ART), the package 10 embedded in the lid 11 comprises the substrate 100; a plurality of passive components 102 mounted at predetermined positions of the substrate 100; a flash memory chip 103; a controller chip 104; a plurality of gold wires 105, 106 for electrically connecting the flash memory chip 103 and the controller chip 104 respectively to the substrate 100; and an encapsulant 107 formed on the substrate 100, for encapsulating the passive components 102, the flash memory chip 103, the controller chip 104, and the gold wires 105, 106.
To prevent a resin compound making the encapsulant 107 from flashing to the conductive terminals 101 on the bottom surface 100a of the substrate 100 during a molding process for forming the encapsulant 107, a current strategy is to encapsulate only an inner portion 110 of a top surface 100b of the substrate 100 with the encapsulant 107, and allow an outer portion 120 surrounding the inner portion 110 of the top surface 100b of the substrate 100 to be exposed from the encapsulant 107. As such, the outer portion 120 is firmly clamped by a mold 12 during the molding process so as to prevent flash-over of the resin compound to the conductive terminals 101 of the substrate 100, as shown in FIG. 1 C (PRIOR ART). For effectively preventing resin flash-over by clamping the substrate 100 during molding, the outer portion 120 of the substrate 100 should be sized at least 1 mm wide to be capable of being effectively clamped by the mold 12, which is thus considered occupying a significant part of the top surface 100b of the substrate 100 having a standard size, thereby reducing surface area for mounting chips and passive components on the substrate 100.
As shown in FIG. 1D (PRIOR ART), the substrate 100 used in the MMC 1 is presumed having an imaginary dotted line d indicating an edge of the fabricated encapsulant 107, such that an area on the top surface 100b of the substrate 100 encompassed by the dotted line d represents the inner portion 110, and an area of the top surface 100b outside the inner portion 110 represents the outer portion 120. An area of the top surface 100b shaded by oblique lines indicates a gate for injecting mold flow of the resin compound to fill the inner portion 110 to form the encapsulant 107 during the molding process. To prevent the mold flow from being affected by the chips 103, 104 and the passive components 102 and avoid uneven mold flow and voids formed in the encapsulant, a current solution is to reduce an area for mounting the chips and passive components on the substrate 100 by limiting the area to being located between two dotted lines e-e parallel to the direction of mold flow (as indicated by arrows), such that the mold flow can pass a region between the dotted line e and a side wall of a mold cavity to effectively avoid formation of voids. The dotted line e is located 3 mm inwardly from an edge of the inner portion 110 of the substrate 100. However, such method of reducing the area for mounting the chips and passive components limits the location and size of the chips and passive components that can be mounted on the substrate. As a result, under a condition that memory chips are enlarged in size with increase in capacity of memory cards, a flash memory chip having large capacity of e.g. 1 Gb is deemed oversized and cannot be accommodated on the foregoing substrate, making the conventional MMC fail to meet the requirement of memory capacity.
Accordingly, U.S. Patent Publication No. 2004/0259291A1 discloses a MMC that eliminates the foregoing problem and is capable of accommodating large chips therein, as shown in FIG. 2A (PRIOR ART). The MMC has such advantage because of using a large encapsulant 20 that covers a substrate 21 (as indicated by a dotted line) and a connective portion outside the substrate 21 to encapsulate chips and passive components (not shown). As such, a mold used in a molding process is allowed to clamp the connective portion rather than a top surface of the substrate 21, thereby making larger chips and passive components able to be mounted on the top surface of the substrate 21. The large encapsulant 20 also prevents formation of voids in the encapsulant 20.
However, conventional saw singulation equipment is not suitably applied to a singulation process of the above MMC with the substrate 21 being completely covered by the encapsulant 20 because the conventional saw singulation equipment can only perform linear cutting but fails to form a chamfer necessary for the MMC. Consequently, a water jetter or a laser cutting technique is required to cut and form the MMC with a desirable shape as shown by arrows in FIG. 2B (PRIOR ART). However, the use of water jetter or laser cutting technique increases fabrication costs and consumes much material in the cutting process, thereby not favorable for a cost-down strategy of the market.